/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.client.example;

import static org.apache.hadoop.hbase.util.FutureUtils.addListener;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicReference;
import java.util.stream.IntStream;

import org.apache.commons.io.IOUtils;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.AsyncConnection;
import org.apache.hadoop.hbase.client.AsyncTable;
import org.apache.hadoop.hbase.client.ConnectionFactory;
import org.apache.hadoop.hbase.client.Get;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.Threads;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A simple example shows how to use asynchronous client.
 */
@InterfaceAudience.Private
public class AsyncClientExample extends Configured implements Tool {

    private static final Logger LOG = LoggerFactory.getLogger(AsyncClientExample.class);

    /**
     * The size for thread pool.
     */
    private static final int THREAD_POOL_SIZE = 16;

    /**
     * The default number of operations.
     */
    private static final int DEFAULT_NUM_OPS = 100;

    /**
     * The name of the column family. d for default.
     */
    private static final byte[] FAMILY = Bytes.toBytes("d");

    /**
     * For the example we're just using one qualifier.
     */
    private static final byte[] QUAL = Bytes.toBytes("test");

    private final AtomicReference<CompletableFuture<AsyncConnection>> future = new AtomicReference<>();

    private CompletableFuture<AsyncConnection> getConn() {
        CompletableFuture<AsyncConnection> f = future.get();
        if(f != null) {
            return f;
        }
        for(; ; ) {
            if(future.compareAndSet(null, new CompletableFuture<>())) {
                CompletableFuture<AsyncConnection> toComplete = future.get();
                addListener(ConnectionFactory.createAsyncConnection(getConf()), (conn, error) -> {
                    if(error != null) {
                        toComplete.completeExceptionally(error);
                        // we need to reset the future holder so we will get a chance to recreate an async
                        // connection at next try.
                        future.set(null);
                        return;
                    }
                    toComplete.complete(conn);
                });
                return toComplete;
            } else {
                f = future.get();
                if(f != null) {
                    return f;
                }
            }
        }
    }

    @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "NP_NONNULL_PARAM_VIOLATION", justification = "it is valid to pass NULL to CompletableFuture#completedFuture")
    private CompletableFuture<Void> closeConn() {
        CompletableFuture<AsyncConnection> f = future.get();
        if(f == null) {
            return CompletableFuture.completedFuture(null);
        }
        CompletableFuture<Void> closeFuture = new CompletableFuture<>();
        addListener(f, (conn, error) -> {
            if(error == null) {
                IOUtils.closeQuietly(conn);
            }
            closeFuture.complete(null);
        });
        return closeFuture;
    }

    private byte[] getKey(int i) {
        return Bytes.toBytes(String.format("%08x", i));
    }

    @Override
    public int run(String[] args) throws Exception {
        if(args.length < 1 || args.length > 2) {
            System.out.println("Usage: " + this.getClass().getName() + " tableName [num_operations]");
            return -1;
        }
        TableName tableName = TableName.valueOf(args[0]);
        int numOps = args.length > 1 ? Integer.parseInt(args[1]) : DEFAULT_NUM_OPS;
        ExecutorService threadPool = Executors.newFixedThreadPool(THREAD_POOL_SIZE, Threads.newDaemonThreadFactory("AsyncClientExample"));
        // We use AsyncTable here so we need to provide a separated thread pool. RawAsyncTable does not
        // need a thread pool and may have a better performance if you use it correctly as it can save
        // some context switches. But if you use RawAsyncTable incorrectly, you may have a very bad
        // impact on performance so use it with caution.
        CountDownLatch latch = new CountDownLatch(numOps);
        IntStream.range(0, numOps).forEach(i -> {
            CompletableFuture<AsyncConnection> future = getConn();
            addListener(future, (conn, error) -> {
                if(error != null) {
                    LOG.warn("failed to get async connection for " + i, error);
                    latch.countDown();
                    return;
                }
                AsyncTable<?> table = conn.getTable(tableName, threadPool);
                addListener(table.put(new Put(getKey(i)).addColumn(FAMILY, QUAL, Bytes.toBytes(i))), (putResp, putErr) -> {
                    if(putErr != null) {
                        LOG.warn("put failed for " + i, putErr);
                        latch.countDown();
                        return;
                    }
                    LOG.info("put for " + i + " succeeded, try getting");
                    addListener(table.get(new Get(getKey(i))), (result, getErr) -> {
                        if(getErr != null) {
                            LOG.warn("get failed for " + i);
                            latch.countDown();
                            return;
                        }
                        if(result.isEmpty()) {
                            LOG.warn("get failed for " + i + ", server returns empty result");
                        } else if(!result.containsColumn(FAMILY, QUAL)) {
                            LOG.warn("get failed for " + i + ", the result does not contain " + Bytes.toString(FAMILY) + ":" + Bytes.toString(QUAL));
                        } else {
                            int v = Bytes.toInt(result.getValue(FAMILY, QUAL));
                            if(v != i) {
                                LOG.warn("get failed for " + i + ", the value of " + Bytes.toString(FAMILY) + ":" + Bytes
                                        .toString(QUAL) + " is " + v + ", exected " + i);
                            } else {
                                LOG.info("get for " + i + " succeeded");
                            }
                        }
                        latch.countDown();
                    });
                });
            });
        });
        latch.await();
        closeConn().get();
        return 0;
    }

    public static void main(String[] args) throws Exception {
        ToolRunner.run(new AsyncClientExample(), args);
    }
}
